The posterior cervical area exhibits a complex anatomy comprising fascia, nerves, and muscles. With the widespread adoption of ultrasound in regional anesthesia, numerous posterior cervical interfascial plane block techniques have been developed in recent years. The injectate spreads along the fascial plane, blocking nerves that traverse the interfascial space after being injected into the target plane. The posterior cervical interfascial blocks have been manifesting the great potential for perioperative analgesia and chronic pain management in the head, neck, and shoulder regions. However, a comprehensive review of these methods as well as their indications, contraindications, and complications remain lacking. This article summarizes the anatomy of the posterior cervical musculofascial layers, highlighting the characteristics of interfascial plane block techniques and their potential limitations. By using the fascial anatomy as an entry point for studying interfascial plane blocks, it enhances our understanding of the mechanisms underlying the efficacy and complications of these block techniques. It not only reviews well-studied blocks such as trapezius plane (TP), multifidus cervicis plane (MCP), inter-semispinal plane (ISP), and erector spinae plane (ESP) block but also includes recently developed techniques from the past 5 years, such as the retrolaminar cervical block, serratus posterior superior intercostal plane (SPSIP) block, and C2 dorsal root ganglion (DRG) “three-in-one” block. The available evidence suggests that while posterior cervical interfascial plane blocks effectively target the dorsal rami of cervical nerves, non-posterior cervical block techniques also exhibit analgesic potential for the posterior cervical region. This review aims to provide insights for further exploration of novel approaches in this emerging field. In conclusion, posterior cervical interfascial plane blocks demonstrate significant clinical value and warrant further development and optimization.

Anatomical variations in nerves are common and can significantly impact ultrasound-guided regional anesthesia. They directly influence needle trajectory, local anesthetic spread, and block efficacy, contributing to procedural failure or complications. However, the literature specifically addressing the clinical implications of neural variations for regional anesthesia remains limited. This narrative review synthesizes evidence on three key aspects: (1) variations of common peripheral nerves and their clinical significance in regional anesthesia (including the terminal branches of the trigeminal nerve, suprascapular nerve, phrenic nerve, lumbar plexus, saphenous nerve, obturator nerve, and sciatic nerve); (2) variations of major vessels relevant to regional anesthesia and their clinical significance in regional anesthesia (including the Adamkiewicz artery and vertebral artery); (3) variations of the spine and spinal nerve roots and their clinical significance in regional anesthesia. This review systematically synthesizes current evidence on these anatomical variations and introduces practical resources, including regional ultrasound guidance and tables correlating specific variants with technical modifications, to enhance ultrasound recognition and clinical decision-making, thereby serving as a valuable reference for clinicians.